External protection system for a liquefied gas storage tank, liquefied gas storage tank comprising it and method for forming said external protection system

Abstract

The present invention relates to an external protection system of a liquefied gas storage tank, a liquefied gas storage tank including the same, and a method of forming the external protection system of the liquefied gas storage tank, the external protection system of the liquefied gas storage tank including: an insulation portion provided on an outer surface of a storage tank body in which liquefied gas is stored; and a protection portion provided on an outer surface of the insulation portion, the protection portion including: a first urea coating layer provided on the insulation portion; a second urea coating layer provided on the first urea coating layer; and a reinforcement layer provided in a portion of an area between the first urea coating layer and the second urea coating layer, including a plurality of reinforcement materials provided to be spaced apart from each other.

Description

Technical Field

[0001] The present invention relates to an external protection system for a liquefied gas storage tank, a liquefied gas storage tank including the same, and a method for forming the external protection system for the liquefied gas storage tank. Background Technology

[0002] Liquefied natural gas (LNG), liquefied petroleum gas (LPG), and liquefied ethylene gas are obtained by cooling natural gas or petroleum gas to extremely low temperatures (approximately -163°C in the case of LNG). Compared to their gaseous state, their volume is significantly reduced, making them ideal for storage and transportation.

[0003] This type of liquefied gas is stored and transported in storage tanks. However, when the liquefied gas is stored in the storage tank and transported, it vaporizes due to the heat outside the tank, causing the internal pressure of the storage tank to rise.

[0004] To address this, conventional methods have involved applying polyurethane foam as a panel to the surface of LPG storage tanks or spraying polyurethane foam to form an insulation layer (e.g., Korean Patent Publication No. 10-0166608). However, when storing LPG, a cryogenic substance, in the tank, thermal stress occurs at the interface between the insulation layer and the tank, damaging the relatively weak insulation layer. Furthermore, the internal temperature of the tank changes when LPG is injected or discharged. Additionally, ships equipped with storage tanks experience significant external temperature variations as they travel from the poles to the equator. These temperature changes can cause the insulation layer to contract or expand, potentially damaging it.

[0005] To address this issue, conventional systems have employed high-strength FRP materials or urea coatings to form a protective layer on top of the insulation layer, thus protecting the exterior of the storage tank. However, due to the temperature variations of the cryogenic liquefied gas stored inside the tank, the external protection system undergoes deformation such as contraction and expansion. In such cases, the insulation layer may delaminate from the tank surface, or the insulation and protective layers within the external protection system may separate from each other, and cracks may occur in either the insulation or protective layer, thereby reducing the insulation effect. Furthermore, when the temperature of the storage tank changes, the difference in thermal expansion coefficients between the insulation and protective layers within the external protection system can damage or deform the insulation or protective layer. Additionally, conventional urea coatings used as protective layers have relatively weak resistance to external forces; therefore, urea coatings are suitable for locations not exposed to external gases.

[0006] Therefore, it is necessary to develop a new type of external protection system that can protect liquefied gas storage tanks from temperature changes, external environment and impact. Summary of the Invention

[0007] The purpose of this invention is to provide an external protection system for liquefied gas storage tanks that can provide stable protection against physical, chemical, and environmental factors, as well as a method for forming the same.

[0008] Furthermore, the object of the present invention is to provide a liquefied gas storage tank including an external protection system for the liquefied gas storage tank.

[0009] To address the aforementioned problems, the present invention provides an external protection system for a liquefied gas storage tank. The external protection system includes: a heat insulation portion disposed on the outer surface of a storage tank body that internally contains liquefied gas; and a protective portion disposed on the outer surface of the heat insulation portion. The protective portion includes: a first urea coating disposed on the heat insulation portion; a second urea coating disposed on the first urea coating; and a reinforcing layer disposed in a portion of the area between the first urea coating and the second urea coating, comprising a plurality of reinforcing materials spaced apart from each other.

[0010] According to one embodiment of the invention, the reinforcing layer is disposed only in the region between the outer surface of the first urea coating 121 and the inner surface of the second urea coating 123, which corresponds to the upper region of the storage tank body.

[0011] According to one embodiment of the invention, the reinforcing material may include a rubber-containing composite sheet.

[0012] According to another embodiment of the present invention, the rubber-containing composite sheet may be a composite sheet containing butyl rubber and fiber sheets or metal sheets.

[0013] According to another embodiment of the invention, the protective portion may further include an ultraviolet blocking layer disposed on the second urea coating.

[0014] According to another embodiment of the present invention, the present invention may further include a drainage path disposed between the lower inner surface of each of the reinforcing materials 122a and the corresponding outer surface of the first urea coating 121.

[0015] Furthermore, the present invention provides a liquefied gas storage tank, the liquefied gas storage tank comprising: a storage tank body for containing liquefied gas; and an external protection system for the liquefied gas storage tank disposed on the outer surface of the storage tank body.

[0016] Meanwhile, the present invention provides a method for forming an external protection system for a liquefied gas storage tank. The method for forming an external protection system for a liquefied gas storage tank includes the following steps: spraying a heat-insulating material onto the outer surface of the storage tank body containing liquefied gas to form a heat-insulating portion; spraying a first urea coating composition onto the outer surface of the heat-insulating portion to form a first urea coating; distributing a plurality of reinforcing materials spaced apart on a portion of the outer surface of the first urea coating to form a reinforcing layer; and spraying a second urea coating composition onto the outer surface of the first urea coating where the reinforcing layer is not formed and the outer surface of the reinforcing layer to form a second urea coating.

[0017] According to one embodiment of the present invention, the present invention may further include the step of forming an ultraviolet blocking layer on the second urea coating using an ultraviolet protective coating composition.

[0018] According to another embodiment of the present invention, prior to the step of forming the reinforcing layer, an additional step may be included: providing drainage channels on the outer surface of the first urea coating corresponding to the lower side of each of the reinforcing materials.

[0019] In this invention, the protective portion formed on the heat insulation portion includes a flexible urea coating and a reinforcing layer formed therebetween, thereby minimizing the occurrence of cracks caused by the contraction and expansion of the cryogenic tank, absorbing displacement caused by temperature changes in the storage tank, and solving potential breakage problems. Attached Figure Description

[0020] Figure 1 A diagram illustrating the external protection system of a liquefied gas storage tank according to an embodiment of the present invention is provided.

[0021] Figure 2 To show in magnified form Figure 1 A sectional view of part A.

[0022] Figure 3 To show in magnified form Figure 1 Sectional view of part B.

[0023] Figure 4 This is a top view showing the arrangement of multiple reinforcing materials spaced apart in the external protection system of a liquefied gas storage tank according to an embodiment of the present invention.

[0024] Figure 5 A side view showing the arrangement of multiple reinforcing materials spaced apart in the external protection system of a liquefied gas storage tank according to an embodiment of the present invention.

[0025] Figure 6 A flowchart illustrating a method for forming an external protection system for a liquefied gas storage tank according to the present invention.

[0026] Figure 7 A photograph illustrating the process of forming a drainage channel when forming an external protection system for a liquefied gas storage tank according to the present invention.

[0027] Figure 8 The diagram illustrates the arrangement of multiple reinforcing materials spaced apart when forming the external protection system for the liquefied gas storage tank of Example 1.

[0028] Figure 9 The diagram illustrates the arrangement of multiple reinforcing materials spaced apart when forming the external protection system for the liquefied gas storage tank of Embodiment 2.

[0029] Figure 10 The results of explaining the thermal structure of the liquefied gas storage tanks of Examples 1 and 2 are shown.

[0030] Explanation of reference numerals in the attached figures Storage tank: T; External protection system: 100; Insulation section: 110; Protection Department: 120; First protection section: 120A; Second protection section: 120B; First urea coating: 121; Reinforcement layer: 122; Second urea coating: 123; Drainage channel: 130. Detailed Implementation

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. These embodiments are provided to illustrate the invention more completely to those skilled in the art. The following embodiments can be modified in many different ways, and the scope of the invention is not limited to these embodiments. Throughout this specification, the same reference numerals denote the same structures.

[0032] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, unless explicitly defined, terms as defined in commonly used dictionaries should not be interpreted ideally or excessively.

[0033] Furthermore, the dimensions and thicknesses of the structures shown in the figures are presented arbitrarily for ease of explanation, and the present invention is not limited thereto. The thicknesses of multiple layers and regions are enlarged in the figures to clearly illustrate them. Moreover, the thicknesses of some layers and regions are enlarged in the figures for ease of explanation.

[0034] Furthermore, throughout the specification, when a part “includes” a structural element, unless otherwise stated, it means that other structural elements may also be included, rather than excluding other structural elements.

[0035] Furthermore, throughout the instruction manual, "above" or "upper part" refers to the case where it is located above or below the object part, as well as the case where it is separated by other parts, and not the case where it is located above the direction of gravity.

[0036] Furthermore, in this specification, terms such as "first" and "second" do not indicate any arbitrary order or degree of importance, but are used to distinguish multiple structural elements from each other.

[0037] Furthermore, in this specification, "liquefied gas" may include all gaseous fuels that are generally stored in a liquid state, such as liquefied natural gas (LNG), liquefied petroleum gas (LPG), and liquefied ethylene gas, which are stored at extremely low temperatures (approximately -163°C). Liquefied gas may include both liquid liquefied gas and vaporized liquefied gas.

[0038] <External Protection System for Liquefied Gas Storage Tanks and its Formulation Method> This invention relates to an external protection system for liquefied gas (LPG) storage tanks, used to ensure the insulation performance of storage tanks that can internally store and transport LPG. This system is applicable to independent LPG storage tanks that are separately formed from the ship's hull structure and manufactured as if mounted on the hull. Hereinafter, the external protection system of this invention will be described using an example of an independent LPG storage tank.

[0039] Figure 1 A diagram illustrating the external protection system of a liquefied gas storage tank according to one embodiment is provided. Figure 2 To show in magnified form Figure 1 Sectional view of part A, Figure 3 To show in magnified form Figure 1 Sectional view of part B.

[0040] like Figure 1As shown, an external protection system 100 for a liquefied gas storage tank according to an embodiment of the present invention ensures the heat insulation performance of the storage tank by protecting the exterior of the liquefied gas storage tank. It includes: a heat insulation portion 110 disposed on the outer surface of the storage tank body T containing the liquefied gas; and a protection portion 120 disposed on the outer surface of the heat insulation portion 110. The protection portion 120 includes: a first urea coating 121 disposed on the heat insulation portion 110; a second urea coating 123 disposed on the first urea coating 121; and a reinforcing layer 122 disposed in a portion of the area between the first urea coating 121 and the second urea coating 123, comprising a plurality of reinforcing materials 122a and 122b spaced apart from each other.

[0041] The following is for reference Figures 1 to 3 The external protection system 100 of a liquefied gas storage tank according to one embodiment of the present invention will be described.

[0042] (a) Insulation section 110 In this invention, the heat insulation part 110 is formed by spraying or attaching heat insulation material to the outer surface of the tank body T, so as to protect the tank T from external heat intrusion and prevent the liquefied gas contained inside from vaporizing.

[0043] The thermal insulation materials that can be used in this invention are not particularly limited as long as they are known in the art. For example, they can be polyurethane foam (PU foam) or compositions thereof.

[0044] (b) Protection Department 120 In this invention, such as Figure 1 As shown, a protective portion 120 is provided on the outer surface of the heat insulation portion 110. This protective portion 120 can block foreign objects such as moisture that may flow in from the outside and prevent damage to the heat insulation portion. In particular, the protective portion 120 can prevent damage to the heat insulation portion 110 or cracking due to pressure rise inside the tank caused by liquefied gas leakage or external impact in extremely low temperature environments. Furthermore, the protective portion 120 can prevent displacement caused by temperature changes in the storage tank.

[0045] This protective layer 120 includes two urea coatings 121, 123 arranged facing each other and a reinforcing layer 122 disposed between a portion of the plurality of urea coatings 121, 123.

[0046] The first urea coating 121 is applied to the outer surface of the heat insulation part 110, and has excellent adhesion to the heat insulation part 110 as a cover, and also has excellent elasticity. Therefore, when the can body T shrinks or expands, it can prevent damage to the heat insulation part 110.

[0047] This first urea coating 121 can be formed by directly spraying a first urea coating composition onto the outer surface of the heat insulation part, but the present invention is not limited thereto. In this case, the first urea coating composition is not particularly limited as long as it is known in the art.

[0048] The second urea coating 123 is disposed facing the first urea coating 121, and is applied to the outer surface of both the first urea coating 121 (without the reinforcing layer 122) and the reinforcing layer 122. This second urea coating 123 exhibits excellent waterproofing, heat resistance, and corrosion resistance, thereby preventing the inflow of moisture and other foreign substances. Furthermore, similar to the first urea coating 121, the second urea coating 123 prevents damage to the insulation layer or the formation of cracks.

[0049] The thickness of the second urea coating 123 is not particularly limited.

[0050] The second urea coating 123 is formed in the same manner as the first urea coating 121. The second urea coating can be formed by spraying the second urea coating composition onto the outer surface of the first urea coating (where the reinforcing layer is not formed) and onto the outer surface of the reinforcing layer, but is not limited thereto. In this case, the second urea coating composition can be the same as or different from the first urea coating composition, as long as it is known in the art, and is not particularly limited thereto.

[0051] like Figure 1 As shown, the reinforcing layer 122 is disposed in a portion of the area between the first urea coating 121 and the second urea coating 123.

[0052] Specifically, such as Figure 2 As shown, a reinforcing layer 122 is formed in a portion of the area between the first urea coating 121 and the second urea coating 123, such as... Figure 3 As shown, no reinforcing layer 122 is formed in the remaining area. This reinforcing layer 122 forms a gap between the first urea coating 121 and the second urea coating 123, thereby forming a gap between the heat insulation portion 110 and the protective portion 120, and can strengthen the protective portion 120. Therefore, when the heat insulation portion 110 shrinks due to the temperature of the liquefied gas contained inside the tank body T, the reinforcing layer 122 can compensate for the corresponding shrinkage, thereby preventing potential damage to the external protection system.

[0053] In particular, when liquefied gas is injected into or discharged from the storage tank body T, the temperature change on the upper side of the storage tank body T is greater than that on the lower side. Therefore, compared to the lower part, the upper part of the storage tank body T experiences greater displacement due to contraction and expansion. Consequently, compared to the lower region of the external protection system corresponding to the lower outer surface, the upper region of the external protection system 100 corresponding to the upper outer surface of the storage tank body T is more likely to delamination from the tank body T, or to experience displacement, damage, or cracking. Therefore, in this invention, as... Figure 1 As shown, the reinforcing layer 122 is disposed in the area between the outer side of the first urea coating 121 and the inner side of the second urea coating 123, which corresponds to the upper part of the tank body T.

[0054] According to one example, the external protection system 100 of the present invention includes a heat insulation portion 110 and a protective portion 120 disposed on the heat insulation portion 110. The protective portion 120 includes: a first protective portion 120A (hereinafter, "upper protective portion"), on which a first urea coating 121, a reinforcing layer 122, and a second urea coating 123 are sequentially laminated on the outer surface of the heat insulation portion 110 corresponding to the upper region of the can body T; and a second protective portion 120B (hereinafter, "lower protective portion"), on which a first urea coating 121 and a second urea coating 123 are sequentially laminated on the outer surface of the heat insulation portion 110 corresponding to the remaining region of the can body T (see reference 120A). Figure 2 and Figure 3 Therefore, the present invention can minimize the separation, damage, displacement, etc. of the external protection system caused by temperature changes in the upper part of the storage tank body T.

[0055] According to another example, such as Figure 5 As shown, the upper region of the storage tank can be the region from the vertex α of the storage tank body that connects to the vertical centerline (e.g., the line of the minor axis) (V-V') of the storage tank body to the low point β of the storage tank body that connects to the first line L1 formed by the horizontal centerline (e.g., the line of the major axis) (H-H') of the storage tank body at an angle of 15-45° (specifically, 20-40°, more specifically, 25-35°).

[0056] The reinforcing layer 122 includes a plurality of reinforcing materials 122a and 122b, which are spaced apart from each other (see reference). Figure 4 and Figure 5 As described above, the present invention divides the reinforcing layer 122 into multiple regions (i.e., multiple reinforcing materials), thereby significantly reducing surface wrinkling of the external protection system compared to forming a large area without dividing the reinforcing layer into regions.

[0057] The arrangement of the multiple reinforcing materials and the shape of the reinforcing materials are adjusted according to the shape of the tank body T.

[0058] As an example, such as Figure 4 As shown, when the shape of the can body T viewed from the top is elliptical, in the central region S1 of the can body, multiple reinforcing materials 122a, which are longer along the width direction (Y-axis direction) of the can body, are spaced apart and arranged in parallel. In the two side regions S2 and S3 of the can body, multiple fan-shaped reinforcing materials 122b can be spaced apart along the circumferential direction (see reference). Figure 4 and Figure 5 ).

[0059] As another example, when the shape of the tank body T viewed from the top is circular, multiple fan-shaped reinforcing materials 122b can be arranged spaced apart from each other along the circumferential direction.

[0060] As another example, when the shape of the tank body T viewed from the top is quadrilateral, multiple reinforcing materials 122a that are longer along the length direction (X-axis direction) or width direction (Y-direction) of the tank body can be spaced apart from each other and arranged in parallel.

[0061] The reinforcing materials 122a and 122b that can be used in this invention are not particularly limited as long as they have adhesive strength (adhesion) and can be easily attached to the first urea coating 121. For example, they can be rubber-containing composite sheets.

[0062] The rubber-containing composite sheet can be a composite sheet comprising rubber, fiber sheets, and / or metal sheets. The fiber sheets can be made of glass fiber or carbon fiber, and the metal sheets can be made of aluminum, iron, or stainless steel, etc., but are not limited to these.

[0063] These fiber sheets and metal sheets can be in the form of a plate or a mesh (grid). However, when the fiber sheets and metal sheets are in the form of a mesh, the reinforcing layer 122 has better flexibility than the plate form, thereby minimizing the deformation of the first urea coating 121 and the second urea coating 123.

[0064] According to one example, the rubber-containing composite sheet can be a composite sheet containing butyl rubber and fiber sheets or metal sheets. The butyl rubber-containing composite sheet has excellent initial adhesion; moreover, the adhesion gradually decreases over time. Therefore, when the reinforcing materials 122a and 122b are butyl rubber-containing composite sheets, over time, the reinforcing layer 122 can peel off from the first urea coating 121, forming a hollow space. Moisture that has seeped in from the outside or generated inside can concentrate in this hollow space.

[0065] In this regard, such as Figure 1 As shown, the external protection system 100 of the present invention may further include drainage channels 130, which are respectively provided between the lower inner surface of each reinforcing material 122a, 112b and the corresponding outer surface of the first urea coating 121 to discharge moisture concentrated in the hollow space formed inside the reinforcing layer 122. The plurality of drainage channels 130 can discharge moisture concentrated in the hollow space formed by the partial peeling (separation) of the reinforcing layer 122 and the first urea coating 121 to the outside of the external protection system.

[0066] The drainage channel 130 is a path for discharging water concentrated internally to the outside, and can be formed using a plate with excellent durability and corrosion resistance in marine environments. The plate can be a metal plate, a plastic plate, etc. According to one example, the drainage channel 130 can be formed from a polyurea plate.

[0067] Specifically, after attaching a board (e.g., a polyurea board) to the outer surface of the first urea coating 121, a reinforcing layer 122 is formed. Then, a second urea coating composition is sprayed and cured. In this case, the board is integrated (bonded) with the inner surface of the cured second urea coating 123, while simultaneously peeling off and lifting from the outer surface of the first urea coating 121. This creates a hollow space (lifting) between the inner surface of the board and the outer surface of the first urea coating 121. In this case, the hollow space is formed in the shape of a hole or similar through which the second urea coating 123 extends along its thickness direction. Thus, the hollow space can serve as a drainage channel 130 to drain moisture concentrated in the hollow space inside the reinforcing materials 122a and 122b to the outside of the external protection system. Therefore, in the external protection system, moisture concentrated in the hollow space inside the reinforcing materials 122a and 122b can be easily drained to the outside through the drainage channel 130 and by gravity.

[0068] Although not shown in the figure, the protective portion 120 may also include an ultraviolet blocking layer (not shown) disposed on the second urea coating 123. The ultraviolet blocking layer has excellent ultraviolet protection properties, thus protecting the second urea coating 123 from ultraviolet light, thereby improving the durability of the external protection system of the present invention.

[0069] The ultraviolet blocking layer can be formed by applying an ultraviolet protective coating composition onto the second urea coating 123. The ultraviolet protective coating composition is not particularly limited to any liquid (coating) containing an ultraviolet protective agent known in the art. Examples of such ultraviolet protective agents include hindered amines, salicylic acid, benzophenone, benzotriazole, and cyanoacrylate ultraviolet protective agents, but are not limited thereto.

[0070] The external protection system for the liquefied gas storage tank of the present invention is applicable to liquefied gas storage tanks on land as well as any marine structure floating and flowing in the sea. In other words, the external protection system for the liquefied gas storage tank of the present invention is applicable to vessels such as liquefied gas carriers or liquefied natural gas regasification vessels (LNGRVs), floating production storage and offloading (LNGFPSOs), or floating storage and regasification units (LNGFSRUs).

[0071] On the other hand, the external protection system of the liquefied gas storage tank of the present invention can be formed by various methods. However, by generating a reinforcing section based on two urea coatings, and by providing multiple reinforcing materials and forming a reinforcing layer in a portion of the area between the two urea coatings, the strength of the reinforcing section can be improved.

[0072] Figure 6 A flowchart illustrating the external protection system of the liquefied gas storage tank of the present invention.

[0073] As an example, such as Figure 6 As shown, the external protection system of the liquefied gas storage tank of the present invention can be formed by a method including the following steps: step S100, forming a heat insulation portion on the outer surface of the storage tank body containing liquefied gas; step S200, spraying a first urea coating composition onto the outer surface of the heat insulation portion to form a first urea coating; step S300, providing a reinforcing layer by spaced provision of a plurality of reinforcing materials on a portion of the outer surface of the first urea coating; and step S400, spraying a second urea coating composition onto the outer surface of the first urea coating where the reinforcing layer is not formed and the outer surface of the reinforcing layer to form a second urea coating. However, the steps are not limited thereto, and the manufacturing process is not performed sequentially, but the steps of each process can be changed or selectively mixed depending on the design configuration.

[0074] The following is for reference Figure 6 The method for forming the external protection system of the liquefied gas storage tank of the present invention will be explained step by step. For the sake of repetition, the description of the structural elements already described will be omitted.

[0075] Step S100: Formation of the heat insulation part A heat insulation portion 110 is formed on the outer surface of the storage tank body T that contains liquefied gas.

[0076] According to one example, in step S100, heat insulation material is continuously sprayed directly onto the exterior of the tank body T, thereby forming a heat insulation portion 110 that is integrally attached to the storage tank body T. As described above, when the heat insulation material is directly sprayed onto the outer surface of the tank body T to form the heat insulation portion 110, compared to the case where heat insulation material pre-formed into a panel shape is attached to the outer surface of the tank body T, there are no connecting parts or fewer, thereby preventing heat loss more accurately.

[0077] If necessary, the heat insulation portion 110 formed on the exterior of the tank body T can be divided into multiple regions. Furthermore, the heat insulation material is sprayed and layered multiple times to form multiple layers of the heat insulation portion 110. In this case, the density of each layer can be adjusted to be the same or different.

[0078] The thermal insulation materials that can be used in this invention are not particularly limited to any polyurethane foam forming composition known in the art.

[0079] On the other hand, as described above, instead of spraying insulation material (e.g., a composition for forming polyurethane foam), panel-shaped insulation material (e.g., a polyurethane foam panel) can be attached to the exterior of the can body T. However, when attaching insulation material, compared to the case of spraying insulation material, it is necessary to additionally perform the process of adding other insulation materials between each insulation material or connecting these insulation materials through a connecting part.

[0080] Although not shown, a step of grinding the surface of the formed heat insulation portion 110 may be performed before performing step S200.

[0081] The grinding process can remove scratches and other defects from the heat insulation part 110, make its surface smooth, and allow for uniform adjustment of the thickness of the heat insulation part 110.

[0082] This grinding step can be performed using techniques known in the art, such as sanding.

[0083] Step S200, the formation step of the first urea coating like Figure 6 As shown, a first urea coating composition is sprayed onto the outer surface of the heat insulation portion 110 formed in step S100 to form a first urea coating 121.

[0084] This step is the same as step S100, whereby the first urea coating composition is continuously sprayed directly onto the outer surface of the heat insulation part 110, thereby forming a first urea coating 121 that adheres integrally to the outer surface of the heat insulation part 110. Furthermore, the first urea coating composition can be sprayed and layered multiple times to form a multilayer first urea coating 121.

[0085] Step S300: Reinforcing layer formation step Multiple reinforcing materials 122a and 122b are spaced apart and placed on a portion of the outer surface of the first urea coating 121 formed in step S200 to form a reinforcing layer.

[0086] According to one example, in step S300, a plurality of reinforcing materials 122a, 122b may be provided on the outer surface of the first urea coating 121 corresponding to the upper part of the can body T, spaced apart from each other.

[0087] In this case, the multiple reinforcing materials 122a, 122b have adhesive force (adhesion) so that they can be easily attached to the first urea coating 121.

[0088] Step S400: Second urea coating formation step A second urea coating composition is sprayed onto the exposed surface of the first urea coating 121 formed in step S200 and the exposed surface of the reinforcing layer 122 formed in step S300 to form a second urea coating.

[0089] This step is the same as step S200, where the composition for the second urea coating is continuously sprayed directly onto the outer surface of the first urea coating 121 (without the reinforcing layer 122) and the outer surface of the reinforcing layer 122, thereby forming a second urea coating 123 in which the first urea coating 121 and the reinforcing layer 122 are integrally attached. Furthermore, the composition for the second urea coating can be sprayed and layered multiple times to form a multilayer second urea coating 123.

[0090] Step S500: Formation of the ultraviolet blocking layer Optionally, the process may further include the step of using an ultraviolet protective coating composition to form an ultraviolet blocking layer on the second urea coating 123 formed in step S400.

[0091] Step S600: Drainage channel formation step Optionally, after step S200 and before step S300, an additional step may be added: drainage channels may be provided on the outer surface of the first urea coating 121 corresponding to the lower side of each reinforcing material 122a, 122b. These drainage channels can respectively discharge moisture concentrated in the hollow space of the reinforcing layer within the external protection system to the outside of the external protection system.

[0092] Specifically, such as Figure 7As shown, the drainage channel 130 has a plate (e.g., a polyurea plate) attached to the outer surface of the first urea coating 121, corresponding to the lower side position of each preset reinforcing material. Then, as shown in step S300, each reinforcing material is spaced apart at preset positions to form a reinforcing layer 122. Step S400 is then performed to spray a second urea coating composition onto the exposed surfaces of the first urea coating 121 and the reinforcing layer 122 and cure it. In this case, the plate attached to the outer surface of the first urea coating 121 becomes integrated (bonded) with the inner surface of the cured second urea coating 123, while the plate peels off from the outer surface of the first urea coating 121 and lifts up. This creates a hollow space (lifting) between the inner side of the plate and the outer side of the first urea coating 121. Figure 7 As shown in section (c), this hollow space is formed in the shape of a hole or the like that extending through the second urea coating 123 along the thickness direction. Thus, the hollow space can form a drainage channel 130 that discharges moisture concentrated on the inner surfaces of the reinforcing materials 122a and 122b to the outside of the external protection system.

[0093] Furthermore, in this invention, when the drainage channel 130 is formed, the outer surface of the upper end of the plate is brought into contact (attached) with the inner surface of the lower side of the reinforcing materials 122a and 122b, so that only the left and right ends of the plate are attached to the outer surface of the first urea coating 121. As a result, the outlet of the drainage channel 130 is located on the lower side of the drainage channel 130, so that the water concentrated in the hollow space can be easily discharged to the outside by gravity.

[0094] Liquefied gas storage tank The present invention provides a liquefied gas storage tank including the aforementioned external protection system.

[0095] Specifically, the liquefied gas storage tank of the present invention includes a storage tank body T for containing liquefied gas and an external protection system (see reference) of the liquefied gas storage tank disposed on the outer surface of the storage tank body T. Figure 1 To avoid repetition of the wall surfaces, descriptions of the structural elements already described will be omitted.

[0096] In this invention, the storage tank body T can store liquefied gas under high pressure and ultra-low temperature conditions. Therefore, the structure of the liquefied gas storage tank body T is simple, and it is robust in terms of impact resistance and liquid tightness. In particular, the storage tank body T can withstand the internal pressure generated by the vaporization of the liquefied gas contained inside. As an example, the storage tank body T can be a pressure vessel.

[0097] Furthermore, the inner surface of the storage tank body T is in direct contact with the extremely low-temperature liquefied gas. Therefore, the material of the storage tank body T can be a metal with excellent low-temperature characteristics, such as steel, stainless steel, nickel alloy steel, aluminum alloy, high-manganese steel, etc., but is not limited to these.

[0098] Furthermore, the cross-sectional shape of the storage tank body T perpendicular to its length direction can be circular, elliptical, or polygonal, and its outer surface can be curved or flat. Therefore, the inner surface of the external protection system 100 can be curved or flat.

[0099] The present invention will be specifically described below through embodiments. The embodiments and experimental examples below are only one form of the present invention, and the scope of the present invention is not limited to the embodiments and experimental examples below.

[0100] Example 1 A polyurethane foam composition is sprayed onto the outer surface of the storage tank body containing liquefied gas and cured to form a heat insulation part made of polyurethane foam. The surface of the heat insulation part is then polished. Next, a first urea coating composition is sprayed onto the outer surface of the heat insulation part and cured to form a first urea coating. Then, a polyurea sheet is attached to the outer surface of the first urea coating, corresponding to the lower side position of each reinforcing material to be installed at a predetermined location. Then, the reinforcing materials are spaced apart and installed at the predetermined positions to form a reinforcing layer 122. In this case, as... Figure 8 As shown, multiple reinforcing materials with elongated shapes are spaced apart from each other in the area corresponding to the center of the tank body, and multiple reinforcing materials with fan-shaped (central angle θ; approximately 30°) shapes are spaced apart from each other in the areas corresponding to the two side portions of the tank body. Then, a composition for the second urea coating is sprayed onto the exposed surfaces of the first urea coating and the exposed surfaces of the reinforcing layer 122 and cured. In this case, the polyurea sheet attached to the outer surface of the first urea coating bonds to the inner surface of the cured second urea coating. Simultaneously, the space created by the polyurea sheet peeling off from the outer surface of the first urea coating forms a hole or similar shape that penetrates the second urea coating along the thickness direction, forming a drainage passage 130 that drains moisture concentrated on the inner surfaces of the reinforcing materials 122a and 122b to the outside of the external protection system. Then, an ultraviolet-protective coating is applied to the outer surface of the second urea coating, thereby manufacturing a liquefied gas storage tank with an external protection system.

[0101] Example 2 like Figure 9As shown, except that a large area of ​​quadrilateral reinforcing material is provided in the area corresponding to the center part of the tank body, and fan-shaped (center angle θ; 180°) reinforcing materials are provided in the areas corresponding to the two sides of the tank body, the same procedure is performed as in Example 1, thereby manufacturing a liquefied gas storage tank with an external protection system.

[0102] Experimental Example 1 To confirm the thermal stability of the external protection system of the liquefied gas storage tank of the present invention, the following experiments were conducted, and the results are presented below. Figure 10 middle.

[0103] like Figure 10 As shown, compared with the liquefied gas storage tank of Example 2, the surface wrinkles of the liquefied gas storage tank of Example 1 are significantly reduced. Furthermore, the bubble size formed on the surface of the liquefied gas storage tank of Example 1 is approximately 11 mm, while the bubble size of the liquefied gas storage tank of Example 2 is approximately 27 mm.

[0104] As described above, the external protection system of the liquefied gas storage tank of the present invention has excellent thermal stability.

Claims

1. An external protection system for a liquefied gas storage tank, characterized in that, include: Insulation is provided on the outer surface of the storage tank body that internally contains liquefied gas; and A protective section is provided on the outer surface of the heat insulation section. The protection unit includes: A first urea coating is provided on the heat insulation part; A second urea coating is disposed on the first urea coating; and A reinforcing layer is disposed in a portion of the area between the first urea coating and the second urea coating, and includes a plurality of reinforcing materials spaced apart from each other.

2. The external protection system for the liquefied gas storage tank according to claim 1, characterized in that, The reinforcing layer is only provided in the area between the outer surface of the first urea coating and the inner surface of the second urea coating, corresponding to the upper region of the storage tank body.

3. The external protection system for the liquefied gas storage tank according to claim 1, characterized in that, The reinforcing material includes rubber-containing composite sheets.

4. The external protection system for the liquefied gas storage tank according to claim 3, characterized in that, The rubber-containing composite sheet is a composite sheet containing butyl rubber and fiber sheets or metal sheets.

5. The external protection system for a liquefied gas storage tank according to claim 1, characterized in that, The protective layer further includes an ultraviolet blocking layer disposed on the second urea coating.

6. The external protection system for a liquefied gas storage tank according to claim 1, characterized in that, It also includes drainage channels respectively disposed between the inner surface of the lower side portion of each of the reinforcing materials and the outer surface of the corresponding first urea coating.

7. The external protection system for a liquefied gas storage tank according to claim 6, characterized in that, The drainage channel is formed using a plate.

8. A liquefied petroleum gas (LPG) storage tank, characterized in that, include: The storage tank body contains liquefied gas; as well as The external protection system for the liquefied gas storage tank according to any one of claims 1 to 7 is provided on the outer surface of the storage tank body.

9. A method for forming an external protection system for a liquefied gas storage tank, characterized in that, Includes the following steps: Insulating material is sprayed onto the outer surface of the storage tank body containing liquefied gas to form an insulating part; A first urea coating composition is sprayed onto the outer surface of the heat insulation part to form a first urea coating; Multiple reinforcing materials are spaced apart on a portion of the outer surface of the first urea coating to form a reinforcing layer; as well as A second urea coating composition is sprayed onto the outer surface of the first urea coating where the reinforcing layer has not been formed and onto the outer surface of the reinforcing layer to form a second urea coating.

10. The method for forming an external protection system for a liquefied gas storage tank according to claim 9, characterized in that, The method further includes the step of forming an ultraviolet blocking layer on the second urea coating using an ultraviolet protective coating composition.

11. The method for forming an external protection system for a liquefied gas storage tank according to claim 9, characterized in that, Prior to the step of forming the reinforcing layer, an additional step is included: providing drainage channels on the outer surface of the first urea coating corresponding to the lower side of each reinforcing material.

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